System and method for winding audio content using a voice activity detection algorithm

ABSTRACT

A system and method for locating a preferable playback start location after a winding or rewinding action in an audio playing device. In response to an adjustment of the playing location for audio content to a desired playing position, the system determines whether at least one non-speech or silent period of at least a predetermined duration exists within the vicinity of the desired playing position. If at least one such non-speech or silent period exists within the vicinity of the desired playing position, the system adjusts the playing position to fall within one of the at least one non-speech period or silent period.

FIELD OF THE INVENTION

The present invention relates generally to voice compression. Moreparticularly, the present invention relates to the use of voicecompression techniques for improving the usability and quality of audioplayback applications.

BACKGROUND OF THE INVENTION

In audio applications on electronic devices, rewinding/winding hasbecome a required feature. In applications such as the RealPlayer, auser is capable of moving forward and backwards through various audiotracks. This feature can be used for a variety of purposes, such as torevisit a portion of an audio book where the user was distracted, or toskip ahead to a desired location within the audio content.

Winding and rewinding is conventionally performed based upon a certaintime duration. Such systems can automatically move backwards or forwardsin a track by a predetermined period of time with each “touch,” or thelength of time can be dependent upon the length of time that a userpresses a “forward” or “rewind” button or icon. It is also possible forthe position in an audio track to be selected arbitrarily, where audioplayback always starts from a selected location in the audio regardlessof the track's content. In other words, in these systems, the playbackposition is not dependent on the audio content of a signal.

To demonstrate this issue, it is helpful to look at the effect ofrewinding on both music content and speech content. If music content isrewinded back by, for example, twenty seconds, playback will then startin the middle of the music, without control of the exact startingposition. Generally, this is not considered to be a significant issuebecause a music signal is usually considered to be a continuous signal.As a result of this fact, the user will usually not lose track of themusic signal, even when playback is started in the middle of a musicsection.

If the audio comprises spoken speech, words, sentences, paragraphs orchapters, on the other hand, the situation is quite different. If suchaudio content is played starting in the middle of a word, sentence,paragraph or chapter, the entire meaning of the speech may be lost, as aperson may not be able to infer the spoken text that exists before theplayback starting point. This problem occurs frequently when traditionalwinding method is used, i.e., when a winding button is pressed and theplaying position of the audio track is moved by an arbitrary timeinterval. In conventional winding systems, there is no control mechanismthat can ensure that audio playing will start at the beginning of aword, sentence, paragraph or chapter, and such a system would be highlydesirable by the user.

Audio content can include a type of indexing feature that is defined bythe producer of the content. For example, the Victor Reader Classictalking book player includes keys that allow the user to easily movefrom one book element to another, permitting the user to quickly go todesired information. In such systems, a user is capable of moving bychapter, section, page, paragraph, book, or other elements that aredefined by the book's producer. However, such a system only permits theuser to wind or rewind to a limited set of predefined locations.

With music content, a user may often select only certain tracks within amusic track collection for playback or play the entire track collectionfrom start to finish. In such situations, the need for winding is notnecessary, although basic winding functionality is usually stillimplemented in such music-specific applications. However, when the audiocontent includes speech, winding and rewinding is substantially moreimportant, because the user is not simply listening to tracks or songsbut is instead interested in “textual context.” For example, when a useris listening to an audio book, he or she may want to listen to specificchapters, paragraphs, sentences or even words in order to obtain thenecessary or desired context of the respective section.

Another method of navigating through audio content is to divide thecontent into individual tracks to enable a listener to easily navigatethrough the document. Individual tracks are easy to access by movingback and forth between tracks. With this technique, the listener canefficiently access a desired section. For example, a listener can firstbrowse various section headings that correspond to various tracks inorder to find the section he or she wants to listen to. The user canthen use the section numbers included with the section headings totravel to the desired section; the section number announced at the startof each section indicates if the desired section is before or after thecurrent track. Once again, however, the user's options for winding andrewinding are limited. Using such a “track” system, for example, a usermay not be able to rewind the audio to hear only a few seconds of soundthat he or she may have missed during the original playing. Instead, theuser would have to go back to, at a minimum, the beginning of the track,regardless of whether the beginning of the track was a few seconds orseveral minutes backwards in time. The user's only other option would beto attempt to manually wind or rewind the audio content, which leads tothe problem of broken words, sentences, etc. discussed above.

It would therefore be desirable to provide a system and method forpermitting the winding and rewinding of audio content that addresses theabove-identified difficulties.

SUMMARY OF THE INVENTION

The present invention provides for an improved system and method foraudio winding and rewinding. According to the present invention, theposition where playback is started after winding or rewinding isselected based upon the underlying audio signal in the audio content.Because speech signals tend to have burst-like characteristics, short“non-speech” period or silent periods exist within speech signal bursts.The present invention uses the presence and absence of bursts to find alocation in the audio content which is not in the middle of a word,sentence or paragraph. The present invention then starts the playback inone of these locations.

The present invention provides for a number of advantages not found inconventional systems. By starting playback in locations that are not inthe middle of words, sentences or paragraphs, the user receives a morepleasant audio playback without having to suffer through annoyingspeech/audio clipping. The present invention allows for the informativeportion of a piece of audio content to be conveyed to the usercompletely when the playback is started, and eliminates the need to haveto wind or rewind again due to the precise location not being correct.As a result, there is a greatly reduced need for continuous iterationsof winding and rewinding until the precise desired location is found, ashas been conventionally necessary on playback devices dating back to thefirst tape recorders. The present invention can be used on a widevariety of electronic devices, including mobile electronic devices suchas mobile telephones.

These and other advantages and features of the invention, together withthe organization and manner of operation thereof, will become apparentfrom the following detailed description when taken in conjunction withthe accompanying drawings, wherein like elements have like numeralsthroughout the several drawings described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a mobile telephone that can be used inthe implementation of the present invention;

FIG. 2 is a schematic representation of the telephone circuitry of themobile telephone of FIG. 1;

FIG. 3 is a representation of a media player/audio player within whichthe present invention may be implemented;

FIG. 4 is a plot showing the burst characteristics of a speech signal;and

FIG. 5 is a flow chart showing the implementation of one embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 show one representative mobile telephone 12 within whichthe present invention may be implemented. It should be understood,however, that the present invention is not intended to be limited to oneparticular type of mobile telephone 12 or other electronic device.Instead, the present invention can be incorporated into virtually anytype of electronic device, including but not limited to laptop anddesktop computers, personal digital assistants, dictating machines,integrated messaging devices, printers, scanners, fax machines and otherdevices.

The mobile telephone 12 of FIGS. 1 and 2 includes a housing 30, adisplay 32 in the form of a liquid crystal display, a keypad 34, amicrophone 36, an ear-piece 38, a battery 40, an infrared port 42, anantenna 44, a smart card 46 in the form of a UICC according to oneembodiment of the invention, a card reader 48, radio interface circuitry52, codec circuitry 54, a controller 56 and a memory 58. Individualcircuits and elements are all of a type well known in the art, forexample in the Nokia range of mobile telephones.

The present invention provides for an improved system and method foraudio winding and rewinding. According to the present invention, theposition where playback is started after winding or rewinding isselected based upon the underlying audio signal in the audio content.Because speech signals tend to have burst-like characteristics, shortnon-speech periods or silent periods exist within speech signal bursts.The present invention uses the presence and absence of bursts to find alocation in the audio content which is not in the middle of a word,sentence or paragraph. The present invention then starts the playback inone of these locations.

It has been estimated that speech activity in audio content, such asaudio books or audio news, can comprise about around 80% of the totalcontent. In other words, about 80% of a selected contact track willcomprise actual speech, while the remaining 20% would comprise periodsof relative silence, such as between paragraphs, or sections of thecontent. For this reason, it is likely that, after any winding orrewinding occurs within a piece of audio content, the playback positionwill be in the middle of a sentence or word, and not in a non-speechperiod or silent period. However, speech signals usually have a hightendency of sound bursts, meaning that even one second of speech mightinclude many short periods of silence. FIG. 4 shows these “bursty”characteristics within a speech signal. As can be observed in thisfigure. There are several short periods that are characterized aspossess a general lack of sound activity, as well as one longer periodof silence

According to the proposed invention, the position where playback isstarted after winding or rewinding is selected based upon the audiosignal. In the present invention, a user first implements generalwinding and rewinding methods to move the playing position to agenerally location. The system then uses this general location as astarting point and then locates a non-speech period that meetspredetermined criteria. This non-speech period is then selected as theactual starting point.

FIG. 3 is a representation of an audio player 100 within which thepresent invention may be implemented. The audio player 100 includes aplay button 102, a stop button 104, and a position control dial 106. Inmany such systems, a user can use a cursor to move the position controldial 106 forward or backwards (referred to herein as winding orrewinding, respectively) through a piece of audio content. The user canthen actuate the play button 102 to begin playing the content at theselected position.

FIG. 5 is a flow chart showing the implementation of one embodiment ofthe present invention. At step 500 in FIG. 5, a user moves the positioncontrol dial 106-of the audio player 100 either forward or backwards toa desired general position. At step 510, the status of a voice activitydetection (VAD) flag is checked around the selected position to beplayed. If the selected position in the audio content is identified asX, for example, the voice activity flag is checked in every speech framethat is in the vicinity of X. The vicinity can comprise, for example,0.5 seconds forward and 0.5 seconds backward from the selected positionX. The vicinity could also comprise “non-symmetrical” time periodsaround the selected position X (i.e., 0.5 seconds backward and only 0.25seconds forward), or the entire vicinity could be before or after theselected position X. One second of audio usually includes several speechframes. For example, speech frames of AMR and AMR-WB codecs are 20 mslong. Therefore, one second of audio signal possesses 50 speech frames.It should be noted that the numerical values discussed herein are onlyexamples and can be altered depending on the exact application, or typeof content. Variations of these numerical values can be used by thoseskilled in the art under the present invention.

It should be noted that, although a VAD flag and algorithm is discussedherein, any suitable or desirable algorithm can be used for detectingwhether certain periods of audio content contain speech or do notcontain speech. For example, current cellular codecs such as GSM AMR orGSM AMR-WB contain algorithms which can be used for this purpose. Inaddition, custom-made algorithms can be used for the implementation ofthe present invention.

At step 520 in FIG. 5, it is determined whether the VAD flags within thevicinity indicate that a sufficiently long non-speech period has beenfound within the investigated time interval. “Sufficiently long” can bebased upon a predetermined time threshold, and “non-speech period” canrefer to the amount of recorded sound being below a predeterminedthreshold. For example, a “non-speech” period can refer to a periodwhere only general background noise and/or background music isdetermined, or it can refer to a complete silent period where no soundis detected at all. Other definitions for “non-speech period” are alsopossible. “Sufficiently long” may depend upon the application being usedand/or user preferences, as well as whether the application and/or theuser wants to wind or rewind word-by-word, sentence-by-sentence orparagraph-by-paragraph. For example, the user may have a preference thatplayback always begins at the start of a paragraph, which would requiresearching for relative long non-speech periods. If the preference werefor the beginning of a word, on the other hand, “sufficiently long”would constitute a shorter time interval. Therefore, the duration of thedesired non-speech period can vary significantly, ranging from as littleas single speech frame (which is usually around 20 ms) to severalseconds (which comprises tens of speech frames).

If there is a sufficiently long non-speech period within the interval,then it is determined whether the exact playing position selected by theuser is set within a sufficiently long non-speech period at step 530. Ifthe exact playing position selected by the user is set within asufficiently long non-speech period, then no adjustment is made to theplaying position at step 540. If the exact playing position selected bythe user is not set within a sufficiently long non-speech period, thenthe playing position is adjusted to occur within the nearestsufficiently long non-speech period at step 550. If more than onenon-speech period is found, then non-speech period closest to theposition X is selected to be the position to start the playback. In oneembodiment of the invention, positions backward or behind from thecurrent position X are preferred so as to not miss the start of thesentence or word of interest to the user. This preference can take avariety of forms. For example, the system first could scan the entireportion of the interval before the selected position first, and onlyscan the remainder of the interval if no sufficient long non-speechperiods exist before the selected position. Alternatively, thispreference can be “weaker” in that the system goes “backwards” only ifthere are two non-speech periods substantially equidistant in time fromthe selected position. Other permutations for such preferences are alsopossible. Additionally, system or user requirements can dictate theexact position within the sufficiently long non-speech period forplayback to start. For example, playback can ultimately begin at thebeginning, midpoint, or end of the non-speech period, or another periodcould also be selected.

If no non-speech periods are found within the designated time interval,then playback is started at the selected position at step 560 in oneembodiment of the invention. In an alternative embodiment, an iterativetechnique may be used instead. Instead of simply choosing the selectedposition, a longer time interval is selected at step 570 and searchedfor an acceptable time interval. This process can repeated a certainnumber of times (i.e., up until a maximum time interval or until thebeginning or end of a track is reached) or indefinitely, with eachrepeat of process involving the increase of the time interval beingsearched. During this process, the required duration of the non-speechperiod can also be increased, if necessary or desired. The concept ofchanging the duration of the non-speech period is based upon the factthat, the longer is the non-speech period, the more significant is thepause in the speech content. Therefore, one can allow more deviationfrom the original playback position X. This depends on whether the useror system desires to find pauses between sentences, chapters or words.For example, for audio books, it may often be desirable to windparagraph by paragraph, in which case the system would attempt to searchfor longer non-speech periods than would be necessary for windingsentence by sentence.

It should be noted that, although particular methods for determiningsilence periods in speech are discussed herein, the present inventioncan also include other methods of differentiating pauses between words,sentences or paragraphs. For example, methods such as utilizingstatistics of spoken speech for different languages can be used toimplement the detection of pauses between words, sentences, paragraphsor chapters. Alternatively, the present invention can be implementedwithout any differentiation between pause types (i.e., words, sentences,etc.), instead simply looking to the nearest silence period from aselected position in accordance with the process depicted in FIG. 5.

The present invention is described in the general context of methodsteps, which may be implemented in one embodiment by a program productincluding computer-executable instructions, such as program code,executed by computers in networked environments.

Generally, program modules include routines, programs, objects,components, data structures, etc. that perform particular tasks orimplement particular abstract data types. Computer-executableinstructions, associated data structures, and program modules representexamples of program code for executing steps of the methods disclosedherein. The particular sequence of such executable instructions orassociated data structures represent examples of corresponding acts forimplementing the functions described in such steps.

Software and web implementations of the present invention could beaccomplished with standard programming techniques with rule based logicand other logic to accomplish the various database searching steps,correlation steps, comparison steps and decision steps. It should alsobe noted that the words “component” and “module” as used herein, and inthe claims, is intended to encompass implementations using one or morelines of software code, and/or hardware implementations, and/orequipment for receiving manual inputs.

The foregoing description of embodiments of the present invention havebeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the present invention to theprecise form disclosed, and modifications and variations are possible inlight of the above teachings or may be acquired from practice of thepresent invention. The embodiments were chosen and described in order toexplain the principles of the present invention and its practicalapplication to enable one skilled in the art to utilize the presentinvention in various embodiments and with various modifications as aresuited to the particular use contemplated.

1. A method of locating a preferable playback start location after a winding or rewinding action in an audio playing device, comprising: in response to an adjustment of the playing location for an audio content to a desired playing position, determining whether at least one non-speech period of at least a predetermined duration exists within the vicinity of the desired playing position; and if at least one non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, adjusting the playing position to fall within one of the at the least one non-speech period.
 2. The method of claim 1, wherein the predetermined duration comprises a designated period of time before and after the desired playing position.
 3. The method of claim 1, wherein, if more than one non-speech periods of at least the predetermined duration exist within the vicinity of the desired playing position, the playing position is adjusted to fall within the non-speech period that is closest in time to desired playing position.
 4. The method of claim 1, wherein, if a non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position before the desired playing position, and if a non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position after the desired playing position, the playing position is adjusted to fall within the non-speech period before the desired playing position.
 5. The method of claim 1, wherein the determining of whether at least one non-speech period of at least a predetermined duration exists within the vicinity of the desired playing position includes checking the status voice activity detection flags for every sound frame that is within the vicinity of the desired playing position.
 6. The method of claim 1, wherein a non-speech period comprises a length of time where any recorded sound does not exceed a predetermined threshold in magnitude.
 7. The method of claim 1, further comprising, if no non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, not adjusting the playing position.
 8. The method of claim 1, further comprising, if no non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, lengthening the duration of the vicinity of the desired playing position; determining whether at least one non-speech period of at least a predetermined duration exists within the lengthened vicinity of the desired playing position; and if at least one non-speech period of at least the predetermined duration exists within the lengthened vicinity of the desired playing position, adjusting the playing position to fall within one of the at least one non-speech period.
 9. The method of claim 8, further comprising: if no non-speech period of at least the predetermined duration exists within the lengthened vicinity of the desired playing position, continuing to lengthen the vicinity of the desired playing position until a non-speech period of at least the predetermined duration is found or until a predetermined number of lengthenings of the vicinity of the desired playing position has been attempted; and if at least one non-speech period of at least the predetermined duration exists within a vicinity of the desired playing position before the predetermined number of lengthenings of the vicinity of the desired playing position has been attempted, adjusting the playing position to fall within one of the at least one the non-speech period.
 10. The method of claim 1, further comprising: after determining that at least one non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, determining whether the desired playing position falls within one of the at least one non-speech period of at least the predetermined duration; and if the desired playing position falls within one of the at least one non-speech period of at least the predetermined duration, not adjusting the playing position.
 11. A computer program product for locating a preferable playback start location after a winding or rewinding action in an audio playing device, comprising: computer code for, in response to an adjustment of the playing location for an audio content to a desired playing position, determining whether at least one non-speech period of at least a predetermined duration exists within the vicinity of the desired playing position; and computer code for, if at least one non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, adjusting the playing position to fall within one of the at least one non-speech period.
 12. The computer program product of claim 11, wherein the predetermined duration comprises a designated period of time before and after the desired playing position.
 13. The computer program product of claim 11, wherein, if more than one non-speech periods of at least the predetermined duration exist within the vicinity of the desired playing position, the playing position is adjusted to fall within the non-speech period that is closest in time to desired playing position.
 14. The computer program product of claim 11, wherein, if a non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position before the desired playing position, and if a non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position after the desired playing position, the playing position is adjusted to fall within the non-speech period before the desired playing position.
 15. The computer program product of claim 11, further comprising computer code for, if no non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, not adjusting the playing position.
 16. The computer program product of claim 11, further comprising, computer code for, if no non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, lengthening the duration of the vicinity of the desired playing position; computer code for determining whether at least one non-speech period of at least a predetermined duration exists within the lengthened vicinity of the desired playing position; and computer code for, if at least one non-speech period of at least the predetermined duration exists within the lengthened vicinity of the desired playing position, adjusting the playing position to fall within one of the at least one non-speech period.
 17. The computer program product of claim 11, further comprising: computer code for, after determining that at least one non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, determining whether the desired playing position falls within one of the at least one non-speech period of at least the predetermined duration; and computer code for, if the desired playing position falls within one of the at least one non-speech period of at least the predetermined duration, not adjusting the playing position.
 18. An electronic device, comprising: a processor; and a memory unit operatively connected to the processor and including: computer code for, in response to an adjustment of the playing location for an audio content to a desired playing position, determining whether at least one non-speech period of at least a predetermined duration exists within the vicinity of the desired playing position; and computer code for, if at least one non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, adjusting the playing position to fall within one of the at least one non-speech period.
 19. The electronic device of claim 18, wherein the predetermined duration comprises a designated period of time before and after the desired playing position.
 20. The electronic device of claim 18, wherein, if more than one non-speech periods of at least the predetermined duration exist within the vicinity of the desired playing position, the playing position is adjusted to fall within the non-speech period that is closest in time to desired playing position.
 21. The electronic device of claim 18, wherein, if a non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position before the desired playing position, and if a non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position after the desired playing position, the playing position is adjusted to fall within the non-speech period before the desired playing position.
 22. The electronic device of claim 18, wherein the memory unit further comprises computer code for, if no non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, not adjusting the playing position.
 23. The electronic device of claim 18, wherein the memory unit further comprises, computer code for, if no non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, lengthening the duration of the vicinity of the desired playing position; computer code for determining whether at least one non-speech period of at least a predetermined duration exists within the lengthened vicinity of the desired playing position; and computer code for, if at least one non-speech period of at least the predetermined duration exists within the lengthened vicinity of the desired playing position, adjusting the playing position to fall within one of the at least one non-speech period.
 24. The electronic device of claim 18, wherein the memory unit further comprises: computer code for, after determining that at least one non-speech period of at least the predetermined duration exists within the vicinity of the desired playing position, determining whether the desired playing position falls within one of the at least one non-speech period of at least the predetermined duration; and computer code for, if the desired playing position falls within one of the at least one non-speech period of at least the predetermined duration, not adjusting the playing position.
 25. The electronic device of claim 18, wherein the at least one non-speech period comprises at least one silent period. 